To investigate the role played by cytokines in the natural history of ARDS by defining 1)the origin of cytokines release, 2)the effect of cytokines on the severity of ARDS, 3)the pathophysiologic role of cytokines in injury and repair of the lungs; and by determining 1)the effect of systemically released cytokines on organ functions 2)the effect of infections on cytokine release 3)the effect of corticosteroid therapy on cytokines release.